Electromechanical switch employing semiconductive diodes formed at the contacts to simultaneously control direction of plural signals



July 13, 1965 E. BELEK ETAL 3 9 ELECTROMECHANIGAL SWITCH EMPLOYINGSEMICONDUCTIVE DIODES FORMED AT THE CONTACTS TO SIMULTANEOUSLY CONTROLDIRECTION OF PLURAL SIGNALS Filed Nov. 28, 1962 2 Sheets-Sheet 1 FIG. 2

P-TYPE S/L ICON N-TVPE SILICON TOOTHER C/RCU/TS A, FIG. 4 v 5/ J \I X 43|I' (5W I 2 2/ 27 llHll ,3 r

:1 L v 'H l 22 4 25 82 E. BELEK MENTOR? A. MAJL/NGER iwm ATTORNEY y 3,1965 E. BELEK ETAL 3,194,986

ELECTROMECHANICAL SWITCH EMPLOYING' SEMICONDUCTIVE DIODES FORMED AT THECONTACTS TO SIMULTANEOUSLY CONTROL DIRECTION OF PLURAL SIGNALS 2Sheets-Sheet 2 Filed NOV. 28, 1962 FIG. 5

FIG. 6

FIG. 7

United States Patent ELECTROMECHANICAL SWITCH EMPLOYING SEMICONDUCTIVEDIODES FORMED AT THE CONTACTS T0 SiMULTANEOUSLY CONTROL DIRECTION OFPLURAL SIGNALS Emil Belch, New Hyde Park, and Anthony Majlinger, LongIsland City, N.Y., assignors to Bell Telephone Laboratories,Incorporated, New York, N.Y., a corporation of New York Filed Nov. 28,1962, Ser. No. 240,602 7 Claims. (Cl. 307-885) This invention relates toelectrically controlled switching devices and more particularly to sucha device utilizing a magnetic field to effect movement of switchcontacts.

Pormany years an important, indeed an essential, element of telephonesystems and other communication systerns has been the electromechanicalswitch or relay. These devices have proven through the years to beeconomical and reliable means for interconnecting circuits. However,such devices as known heretofore function only as means for interruptingor completing current paths, and do not have the ability to segregatecurrent flow on the basis of polarity or bias.

Notable improvements in communication systems are constantly being made,particularly with regard ,to speed and perfection of transmission, andthese changes have, of course, been accompanied by some increase incomplexity of the various circuits involved. This has, in turn, resultedin increasing demands on the relays utilized, particularly with regardto their speed of operation and ability to control a multiplicity ofcircuits without un due increase in size.

Accordingly, it is an object of our invention to improve the performanceof an electromechanical relay or switch.

Another specific object of the invention is to accomplish simultaneouscontrol of a plurality of separately biased circuit paths by a singlerelay operation thereby materially increasing the eif-ective over-alloperating speed of the relay.

A still further object of the invention is to control the direction ofcurrent flow through closed relay contacts.

In the above and subsequent description the terms relay and switch areused interchangeably.

, In accordance with one specific embodiment of our invention a reedswitching device is provided with asymmetric conductors, such as diodeelements, built into the reed contacts. Three reed springs are provided,two outer springs projecting from one end of the enclosing vessel ortube, and a common central spring projecting from the opposite end ofthe enclosing tube with its free, or contact, end positioned between thefree ends of the respective outer springs. The diode elements arepositioned at both contact surfaces of the common central spring, and,when the three springs are pulled together through normal operation ofthe switch, particular combinations or isolations of the circuitsconnected to the respective reeds are attained depending upon theparticular polarization of the respective diodes with regard to theopposed outer reed. Since a single circuit closure of the device cancontrol a plurality of difierently biased or polarized current paths, iti obvious that the structure embodies inherent advantages both from thestandpoints of effective increases in speed and effective reduction ofsize requirements.

In accordance with another specific embodiment of the invention theover-all arrangement is generally similar to that above described exceptfor the fact that the common central spring carries at its free end acylindrical member with aplurality of diode elements positioned aroundthe peripheral surface thereof; a corresponding number of circularlyarranged outer springs, when pulled together by normal operation of therelay, make contact engagement with the respective diode elements.

A feature of the present invention is asymmetric relay contacts so poledas to obtain various desired circuit relationships through a singleenergization of the relay.

A further feature of the invention, as exemplified in one of thespecific illustrativ embodiment thereof, is means for so supporting aplurality of diode contact members in relation to a corresponding numberof contact springs that full and complete enagement results between allrespective opposed members when the relay is operated, even thoughslight positional irregularities may exist in the structure.

A still further feature of the invention is a single diode contactpositioned on the common center spring of the switch and effective as anasymmetric element only with regard to current fiow between the commoncenter spring and the opposed outer springs.

A full understanding of the arrangements contemplated by the presentinvention as well as an appreciation of the various advantageousfeatures thereof may be gained from consideration of the followingdetailed description in connection with the accompanying drawing inwhich:

FIG. 1 is a side elevation, in partial section, of one specificillustrative embodiment of the invention;

FIG. 2 is an enlarged end view taken on line 2-2 of FIG. 1 showingparticularly the arrangement of the contact members on the reed springs;

FIG. 3 is a schematic showing of the current paths resulting from oneparticular arrangement of the asymmetric contacts, the switch beingenergized to engage the contacts; I

FIG. 4 is a schematicshowing of the current paths resulting from anotherarrangement of the contacts whereby the action of a polarized relay isattained;

FIG. 5 is a schematic showing of an embodiment of the invention whereina single diode contact is positioned on the common center spring;

FIG. 6 is a side elevation, in partial section, of another specificillustrative embodiment of the invention wherein a plurality of diodecontacts are positioned on a cylindrical member carried by the centerspring; and

FIG. 7 is an enlarged end view taken on line 7-7 of FIG. 6 showingparticularly the arrangement of the contacts on the cylindrical memberand on the reed springs.

Referring now to the drawing and first to FIGS. 1 and 2, there is showna glass sealed reed switch which is generally similar in certainrespects to that disclosed in United States Patent 2,289,830, issuedJuly 14, 1942, to W. B. Ellwood. The reed switch comprises three reedspring members 11, 12 and 13 of magnetically soft material sealed withintubular glass vessel 14. The two opposed outer reed springs 11 and 12extend from one end of the vessel 14 while the common central spring 13extends from the opposite end of the vessel with its free or contact endpositioned between the free ends of the respective outer springs.Energizing winding 17 surrounds vessel 14 and is provided with suitableterminals (not shown) for connection in the external circuit. (It willbe understood, also, that each reed spring is provided with suitableterminals for connections to the external circuits.) Norm-ally, that isin the absence of controlling flux, the opposed free ends of reedsprings 11 and 12 are held in separated position and out of contact withspring 13 by the inherent spring bias of the reeds. When winding 17 isenergized the resulting flux acts to pull reed springs 11 and 12 towardeach other whereby to engage the respective opposed contact surfaces ofcommon center reed spring 13. The outer reed springs 11 and 12 areprovided with respective contact points 21 and 22 of suitable material,for example, palladium or gold. Center spring 13 is provided with twodiode contacts, diode 23 being positioned on the upper face of the reedspring and diode 24 being positioned on the lower face thereof. Thesediodes are preferably of the semiconductor junction type and, as shownmore clearly in the enlarged view of FIG. 2, each comprises in thespecific illustrative embodiment a section of p-type silicon and asection of n-type silicon in junction.

It is well known in the art that rectifying contacts can be made betweentwo semiconductors, such as silicon of opposite conductivity types, thedirection of easy flow being that for which the p-type is positive andthe n-type negative. (See Editorial Note Regarding Semiconductors, BellSystem Technical Journal, vol XXVHI, No. 3, July 1949, page 335. Suchrectifiers are discussed further in the articles On the Theory of theA-C Impedance of a Contact Rectifier and The Theory of pn Junctions inSemiconductors and pn Junction Transistors in the above volume, pages428 and 435, respectively.)

Diode contact 23 is provided on its upper surface with metallicelectrode 27 and, similarly, diode contact 24 is provided on its lowersurface with metallic electrode 28. These electrodes may be of anysuitable material, for example, gold or palladium.

As pointed out above, when coil 17 is energized in the normal way, theresulting flux draws the outer reed springs 11 and 12 together to engagecommon reed spring 13 whereupon springs 11 and 13 are electricallyconnected through contact point 21, electrode 27 and diode 23, andsprings 12 and 13 are electrically connected through contact point 22,electrode 28 and diode 24. By relative positioning of the respectivep-type and n-type sections each diode may be polarized or biased asdesired whereby to obtain particular combinations or segregations ofcurrent paths through the switch.

One contemplated arrangement of the diodecontacts whereby to attain aparticular arrangement of current fiow paths, is shown schematically inFIG. 3. In considering the arrangement illustrated in FIG. 3 it will beassumed for purposes of description that the normal direction of currentflow is from ground to battery. As schematically indicated, diodes 23and 24 have been so directed or polarized that the direction of easyflow is from the respective outer reed spring to the common centerspring. That is, the diode elements are polarized symmetrically withregard to the center spring and in respectively opposite directions.Accordingly, when the switch is operated and the contacts engaged, twoindependent current flow paths are set up, one path from ground, reedspring 11, contact point 21, electrode 27, diode 23, reed spring 13, andthrough the load resistor 41 to battery, and the other path from ground,reed spring 12, contact point 22, electrode 23, diode 24, reed spring13, and through load resistor 41 to battery. The particular polarizationof the diodes illustrated provides segregation of the respective currentpaths in reed springs 11 and 12 which is here assumed to be desirablesince the path through spring 12 is associated by way of lead 42 withcertain other circuits (not shown) with which the path through spring 11is not concerned.

Referring now to FIG. 4 there is schematically shown a differentarrangement of the respective diodes whereby the action of a polarizedrelay is attained. Here again a normal direction of current flow fromground to battery is assumed, and for purposes of description anenergizing coil 43 has been shown schematically together with energizingpaths therefor. It will be assumed that, as indicated schematically,both diodes are directed or polarized in a downward direction withrespect to the reed springs. It will be assumed, further, thatrespective pairs of contacts All and A2 and B1 and B2, are coupledmechanically. Assuming, first, that contacts Al and A2 are closed, theswitch is operated by flux resulting from energization of coil 43, and afirst path is completed from ground, make contact A2, load resistor 44,reed spring 11, cond tact point 21, electrode 27, diodes 23 and 24,electrode 2%, contact point 22, reed spring 12, load resistor 47 tobattery. In this instance there is no current flow in reed spring 13since cont act B2 is open.

Assuming now that contacts B1 and B2 are closed instead of contacts Atand A2 as just described, a second path is now completed from ground,make contact B2, reed spring 13, diode 24, electrode 28, contact point22, reed spring 12, load resistor 47 to battery. Flow of current fromreed spring 13 to reed spring 11 is blocked by diode 23 because of itsparticular direction or polarization, so that interference with anyother circuits connected by way of lead 51 is prevented.

Referring now to FIG. 5, there is shown schematically an arrangement inaccordance with which a single diode contact 52 is provided on commoncenter spring 53. Outer springs 54 and 57 are provided with contactpoints 58 and '71, respectively, which may be, for example, gold orpalladium. Diode contact 52, as in the instances described above,comprises sections of semiconductor material of respectively oppositeconductivity types, that is, n-type and p-type, but it will be observedthat the arrangement is such that the path between outer reed springs 54and 57 is completed through one section only. (In the specificillustrative embodiment, the path is completed through the n-typesection.) Accordingly, the path between the two outer springs isnonasymmetric. However, with regard to the respective paths betweenouter reed spring 54 and center reed spring 53, and outer reed spring 57and center reed spring 53, here the complete diode 52, n-type plusp-type, is involved so that the paths are asymmetric, the direction ofeasy fiow being determined by the relative positioning of the twosections. For example, the polarization of the diode 52 may be soestablished that when the switch is closed a first directional path willbe closed from outer reed spring 54, contact point 58, electrode 61,diode 52, to center reed spring 53, and a second directional path willbe closed from outer reed spring 57, contact point '71, electrode 62,diode 52 to center reed spring 53. At the same time a nondirectionalpath will be maintained between outer springs 54 and 57, but there willbe no transmission from the common spring 53 to either outer springs 54or 57.

Referring now to FIGS. 6 and 7, the device there illustrated is ofgenerally similar form to that of FIG. 1. However, in the device ofFIGS. 6 and 7, provision is made for a larger number of outer reedsprings, four reed springs 72, 73, 74 and 77 being shown in the specificillustrative embodiment. These reed springs are provided with respectivecontact points 78, 81, 82 and 83 of suitable material, for example goldor palladium. The four outer reed springs extend in evenly spacedcircular relationship from the left-hand end of enclosing tube or vessel84, and it is obvious that a different number of springs than the fourillustrated may be provided as occasion arises.

Common center reed spring 87, which projects from the right-hand end ofthe vessel 84, is preferably round in cross-section whereby to promoteflexibility in all directions perpendicular to its longer axis for apurpose discussed subsequently. A cylindrical element 83 of suitableconductive material is mounted on the free end of reed 87 and supports aplurality of diode contacts equal in number to, and respectivelyassociated with, the outer reed springs. Each diode contact, as abovedescribed, comprises two sections of semiconductor material ofrespectively opposite conductivity types, n-type and p-type, and eachdiode contact assembly is provided with a siutable rnetallic electrode,for example of gold or palladium. Thus diode 101, which is opposed tocon-tact point 78, is provided with electrode 192; diode 1%, which isopposed to contact point 33, is provided with electrode 164; diode ltld,which is opposed to contact point 81', is provided with electrode 1&7;and diode llli, which is opposed to contact point 82, is provided withelectrode 112.

Normally, that is, in the absence of controlling flux, the outer springsare held out of contact with cylindrical element by their inherentspring bias. When coil 113 is energized, however, the resulting fiuxacts to .pull the free ends of all the reed springs into engagenent.With the provision of a relatively large number of rec springs it isrecognized that instances of imperfeet matching of opposed contacts mayoccasionally result due to cit-center mountings or other manufacturingimperfections. However, by virtue of the novel arrangement contemplated,a perfect engagement of all the op posed contacts is assured. Asmentioned above, common center spring 87 is designed to provideflexibility in all directions perpendicular to its :longer axis.Accordingly, as coil H3 is energized and the resulting flux acts tobring the free ends of the reed springs into contact, cylinder 88 willbe free to wobble slightly under the influence of the flux whereby toattain firm and even contact between all diode electrodes and opposedcontact points even though the resulting combination may necessarily beslightly off-center for attainment of such result. T his is aparticularly valua le feature, permitting as it does successfulapplication of a multiple contact arrangement of the nature disclosedwithout the necessity of unduly stringent manufactuing requirements withregard to spring spacing and mounting.

it will be understood that various polarizations of the diode contactsprovided in the embodiment just described may be utilized to obtaindesired current paths. Also, it will be understood that diode contactsmay be provided on some, or all, of the outer reed springs as dedesired.Also, it desirable, other types of asymmetric conductors may be utilizedin the various embodiments of our invention in place of thesemiconductor diode eleinents disclosed.

it is to be understood that the above-described arrangements areillustrative of the application of the principles of the invention.Numerous other arrangements may be devised by those skilled in the artwithout departing from the spirit and scope of the invention.

What is claimed is:

i. A switching device comprising a pair of spring contact membersmounted in parallel relationship with their opposed contact portionsnormally held in separated position by inherent spring bias, a thirdspring contact member mounted with its free end positioned between therespective contact portions of said pair of spring contact members, adiode element positioned on both major surfaces of said free end of saidthird spring contact memher, and means for drawing together said opposedcontact portions of said pair of spring members whereby to attainengagement of said diode elements and said opposed contact portions. I

2. In a switching device the combination defined by claim 1 furthercharacterized in that said diode elements are polarized symmetricallywith regard to said third spring contact member and in respectivelyopposite directions.

3. in a switching device the combination defined by claim it furthercharacterized in that said diode elements are polarized in the samedirection and unsymmetrically with regard to said third spring contactmember.

4-. A switching device comprising a tubular enclosing vessel, aplurality of spring reed contact members sealed in one end of saidvessel and extending therefrom in evenly spaced circular relationshipinto said vessel with their respective free ends held in separatedposition by inherent spring bias, an additional spring reed membersealed in the other end of said vessel and extending therefrom into saidvessel with its free end positioned substantially in the center of thearea encompassed by the free ends of said plurality of spring reedcontact memhers, a plurality of asymmetric conductors equal in numaclaim t further characterized in that said asymmetric conductorscomprise semiconductor diodes.

s. in a switching device the combination defined in claim 4 furthercharacterized in that said supporting means comprises a cylindricalelement of conductive material with said asymmertic conductors space-daround the peripheral surface thereof.

7. in a switching device the combination defined in claim 6 furthercharacterized in that the arrangement of said additional spring reedmember is such as to promote flexibility thereof in all directionsperpendicular to its longer axis.

References Cited by the Examiner UNITED STATES PATENTS 2,289,830 7/42Ellwood 20Q-87 2,959,717 11/60 Conger 317148.5

ARTHUR GAUSS, Primary Examiner.

1. A SWITCHING DEVICE COMPRISING A PAIR OF SPRING CONTACT MEMBERS MOUNTED IN PARALLEL RELATIONSHIP WITH THEIR OPPOSED CONTACT PORTIONS NORMALLY HELD IN SEPARATED POSITION BY INHERENT SPRING BIAS, A THIRD SPRING CONTACT MEMBER MOUNTED WITH ITS FREE END POSITIONED BETWEEN THE RESPECTIVE CONTACT PORTIONS OF SAID PAIR OF SPRING CONTACT MEMBERS, A DIODE ELEMENT POSITIONED ON BOTH MAJOR SURFACES OF SAID FREE END OF SAID THIRD SPRING CONTACT MEMBER, AND MEANS FOR DRAWING TOGETHER SAID OPPOSED CONTACT PORTIONS OF SAID PAIR OF SPRING MEMBERS WHEREBY TO ATTAIN ENGAGEMENT OF SAID DIODE ELEMENTS AND SAID OPPOSED CONTACT PORTIONS. 